Amplifying horn



Sept. 29, 1925. 1,555,609

F. J. REICHMANN AMPLIFYING HORN Filed June 25, 1923 Patented Sept. 29, 1925.

- UNITED' STATES.

- rum: .1.

or cmcnoo, rumors.

.mmrymo nomr.

Application filed June 25,

To-all concern:

Be it known that I, Fnaifx J. REICHMANN,

citizen of the United States, residing at Chicago, in the countyof and State of Illinois, have invented certain new and useful lmprovements' -in an Ampli mg Horn; and I do hereby declare the fol ow- However, when amplifying horns are used in high] ing to be a full, clear, and exact description of the invention, such as will enable others 7 skilled in 'the art to which it appertains to .make and use the same. v My invention relates to amplifying horns particularly suitable for use in connection with; radio-receiving apparatus, loud speakingtelephone. receivers, phonogra hs and' the -like for amplifying the enntte sounds and projecting them in a predetermined general directzon, Amplifymg horns for such purposes have long been employed in connection with phonographs where the concealing of the horn permits it to be built of uite thick material, where no attention needs to be paid to an artistic appearance, and where an excessive weight of the horn is not objectio able since the horn is ermanently supported within a strong cabinet.

connection with radio receiving outfits, it is desirable-that these shouldbe sufiicient y light so as to be readily portable and that they should be .of artistic configurations. These new requirements bar the use of am lifyinghorns constructed after the genera manner of those employed in modern phonographs.

So also, when amplifying horns are used for magnifying the reproduction of a spoken message, as in the case of loud speaking telephones employed for paging guests in hotels, a distortion of the tone qualities is immaterial as long as the enunciation is suflicientl clear to make the words understood. owever, since wireless receiving outfits are used largely for receiving musical renditions, it is highly important that distortions of the tonal effects, either by an undue accentuation of tones of certain pitch ranges or otherwise, should be avoided.

is requirement has not been met in the amplifying horns now in common use, since metal horns (unless so heavy as to lack the desired portability) will vibrate bodily in response to high notes, while wooden horns will do the samein response to notes of lower pitches, and in either case the ac centuating of a certain range of notes will the shape of the horn, thereby 1823. Serial No. 647,614.

distort the music which is being amplified by the horn. On theother hand, a horn inade of a soft and sound-deadenin 'terial will absorb so much of the 801m as to reduce the amplifying effect which is due to annulling the advantages which such a horn would other-v wise possess on account of its not accentuating tones of selected pitch ranges.

Iy invention aims to overcome the above mentioned objections to horns made of the heretofore customary materials by providing an amplifying horn' made of sounds deadening and sound-vibratory material so intcrmingled and combined as to avoid any pitch accentuation (at least within the common range of voice and music transmission) without causing any considerable sound absorption. More partieularl it aims to provide amplifying horns ma e of a composition which has as one of its ingredients a material with air cells of such microscopic proportions that these air cells will have a sound-deadening efl'ect -to the desired ex-' tent whenthcsaid ingredient is distributed in finely divided form through a composition whose other ingredients are good sound -transmitters.

That is to say, it aims to provide a horn having in its compositionso large a proportion of intimately intermingled cellular and air-filled particles as to reduce both the transverse sound transmission through the horn. and the bodily vibration of the latter, high sound-reflecting eilicicncy and while having the strength and elasticity required for enabling the horn to withstand rough handling t also aims 'to provide a horn of this class which can readily be manufactured in highly artistic sha es and with any desired thickness of wall without employing a core, which willreudilypermit any surface irregularities or roughnesses due to defacts in the manufacture to ing the process of manufacture, which can readily be provided with surface coatings of any desired coloring both for the sake of appearance and for increasing the sound be corrected durwhile still having a lllll the horn of my invention can readily be made, namely a form which is difiicu t to duplicate in most materials and particularlyso in a thin walledform.

- Fig: 2 is a 'centraland vertical section through the same horn.

Fig. 3 is a greatly magnified transverse section of a wall portion of the horn, showtion formed of an inherently resonant and somewhat resilient binder intimately intermingled witha sound-deadening material. For" the latter, I preferably employ a thin walled and cellular air-tilled material in the form of infusorial earth ground to pass through a 150 or 200 mesh screen, desirably securing this infusorial earth from a locality I (such as California) in which the same can be obtained in a variety havingthe quite low specific gravity due -to an unusually large air content. For the binder I desir- .ably employ a gelatinous type, such as a hide stock glue, and I render this resilient by a suitable admixture of other ingredients. After moldinga'horn from these ingredients properly proportioned to secure the above described desirable acoustic effect, I desirably provide both the-interior and the exte-' rior surfaces of the born with a suitable glossy and sound reflecting coating, such as a lacquer of any desired color.-

In manufacturing my amplifying horn, I may thoroughly intermingle from sixty to sixty-five parts by weight of finely ground infusorial earth with a liquid solution composed of about forty parts of ground glue, eighty to one hundred parts of water, and about ten parts each of commercial glycerin and of a socalled non-drying oil. This mixture when well intermingled at a temperature of about 150 F. is poured into a suitabl shaped mold, suchas the mold 1 of Fig. 2, t to moldbei'ng plugged'at the bottom and held in such a position that the liquid mixture entirely [ills the same. The mold itself can readily be made of ordinar plaster of Paris from a model correspon ing in general shape to the exterior of the desired horn but having its linear dimensions about oneseventh greater than those of the proposed finished horn, so as to allow for the shrinkage. It made of plaster of Paris, the interior of the mold is first coated with a film for preventing the resulting solidcomposition' from adhering to the mold, for which purpose I may employ a mixture of one part of stearic acid with ahout'three parts of kerosene.

The liquid mixture as poured into the mold l. l ft in lhesame for a suflicient length of tznuu:- pt-rmit the outer portion thereof to congeal against the surface of the mold in a layers. For example, I may allow the initial layerto cool within the mold forabout a .mmute, or to an extent insutlicient for loosenin it from the mold.-- I then fill the bore of tie initial layer with diluted formalin and allow this to stand for-about ten 'minutcs, during which time the formaldehyde which forms the active constituent of the formalin renders the glue adjacent to the inner surface of the thin molded horn insoluble, thereby-preventing the initial layer from being dissolved by liquid mixture introduced afterwards for forming the next layer. I then draw oil the formalin Solution and allow-the thin'molded-horn to stand within themold for ten or fifteen minutcs, thereby permitting the excess of formalin to evaporate from its inner surface,

after which I proceed as before by pouring.

a new quantity of the liquid'mixture into the mold and thereby. depositing a second layer inside the first. The same general roccdure can be continued for forming at ird layer if desired, although I have found that with the composition proportioned as above described forafl'ordin the desired acoustic properties, I -'can rea lly produce horns of ample strength in'large commercial sizes"- with onlytwo layers.

suitable supports after being withdrawn fronrthe mold.

The amplifying born as thus produced has decided advantages over one made from the previously employed compositions from an acoustic standpoint,'as I have found by my ex eriments that it is unusually effective in de ivering the amplified tone at its mouth and in avoiding an interference with the amplified tones h a resonant vibration of the horn itself. hile I have not'entirely determined the reasons for this superiority, the following explanation seems to be in accordance with recent investigations on I sound transmissions.

In amplifying sound while also guiding it from its smaller end to its mouth, the horn effects the amplification by the reflection of sound within its bore, this bore being of: a size gradually increasing in a desirably logarithmical proportion. At the same time, the material of the horn acts After the horn hasbeen molded to the desired thickness, it is althe general principles involved in the trans 7 mission of sound through partitions should apply to an amplifying horn as effecting its 'efiiciency. Investigations on the soundproofing of partitions haveshown that a-irfilled materials donotim'brate as readily as cessively through quite different substances. In my compositiomfone of the ma n ingredicnts isinflisorial earth, also known asdiaearth or kieselguhr, .-a mineral which is noted for its microscopic cellular structure, and its fine grained consistency. This material, even whenground to pass through a, sc'reenof 150 to 200 mesh (in -which grade of'fineness I desirably use it) still shows air cells under the microscope, or in other words,'each such fine particle of.it has air confined in. a large number of cells within it. Hence, a sound wave .in passing through such a particle is modified when passing from a wall of the cell to the air within-it and this wave ismodified again when' passing from the confined air to the opposite cell wall. Moreover, the cell walls themselves are quitethin and of low sound conductivity so that their poor conducting of sound cooperates with the modification of the. sound waves when changing ironicell walls to air (and vice versa) in making the infusorial earth a good sound deadening material. I

If the horn yvere made entirely of this ingrcdient, it would unduly absorb and dampen the sound, but such an effect is oilset by the inherent resonance and sound reflecting quality of the binder employed for making a solid composition with the infusorial earth as its main body portion. That is to say, by suitably proportioning "and intimately combining such a material of high sound-deadening characteristics with a. binder which by itself would be a good sound conductor and resonator, I produce a horn which is neither decidedly resonant nor sound-absorbing and which might be designated as neutral in these respects. That is to say, I produce a horn which will not readily vibrate as a unit and which therefore will avoid the undesirable accentuating of some. one portion of the range of tones which are being amplified.

The considerable air content together with the low specific gravity of the cell walls of the infusorial earth also reduce the specific gravity of the finished composition, so that. my amplifying horn is relatively quite light and readily portable. So also, by employing a binder which affords a high reflecting surface, I secure the desired sound lrllvrtion within the horn and 1 can readily increase this by the inner coating of lacquer or the like after the manner shown in Fig. 3. By starting with finely ground infusorial earth and thoroughly interuiingling this with the dissolved glue, I secure a composition of quite uniform texture and by having a suitable proportion of a resiliency iniparting ingredient mixed w ththe glue, '1" secure that toughness in the horn which will prevent it from cracking or chipping even if roughly handled, while the vibrationdeadening effect of the air fillings of the cellular infusorial'earth prevent 'this'iesili-.

(ncyfrom imparting an uiulesirable reson -ance to the horn. Moreover, by employing such proportions of the ingredients as those above recited, I can produce amplifying horns of quite large sizes and ample strength with unusually thin walls.

Vith an amplifying horn thus, produced, the layers blend integrally into each other,so that tliedivision between the fir t layerf2 and the second layer 3 (as indiratedsby the dotted line 5 intlie magnified section of" Fig. 3) cannot be discerned, and a relatively, thiii inner coating 4 of lacqlu-r-is'ample. Thanks to the flexibility which such a horn possesses when only partly dried, it can readily be removed fl0lll such a. mold as that shown in Fig. 2 without even withdrawing the air vent plug 6 or the. drainage plug 7 which may be employed to facilitate the use of such a mold. v However, while I have mentioned desirable ingredients in proportions which I have found highly practical, I do not wish to be limited to these or to the manufacturing methods above recited, it being obvious that spirit of my invention or from the appended claims. Neither do I wish to be limited to the use of my novel amplifying horn in connection with sound reproducing devices.

1 claim as my invention:-

l. A sound aiuplif ing horn made entirely of a molded composition having a highly cellular mineral sound deadening material as its preponderaut ingredient and having a substantially uniform wall thickness throughout its length.

.2. A sound amplifying horn having its main wall portion made of i solid and uniform composition whose rhiefingredicnts are a highly cellular sound deadening material and a binder penetrating the cells of the aforesaid material.

2;. A sound amplifying h'orn having a relatively thin walled hotly made of a solid composition comprising a sound deadening material and a simml-vibratory binder comhined in linclj dividedand'intiinately in ermingled form and in sat-1i proportions as to make lhe resulting hor'n neither integrally sound-vibratory nor sound-deadening 4. A sound amplifying horn having a rel- I no "consisting mainly of finely composition consisting mainly of 'a finely ound mineral cellular material and a wall thickness throughout;

' 6. A sound amplifying horn made of a composition consisting mainly of infusorial earth and a gelatinous binder.

7. A sound amplifying horn made of ,a composition consisting mainly of finel ground infusorial earth intermingled wit a smaller amount by weight of a gelatinous binder. I

8. A sound amplifying horn composed mainly of finely ground infusorial earth,

intermingled with a smaller amount by weight of a gelatinous binder and of an ingradient fol-enhancing the. resiliency ofthe gelatinous -binder.

inder, and having a substantially uniform 9. A sound amplifying horn composed mainly of finely divided infusorial earth 111- timately intermingled with the elatinous binder and having a'relatively thin coating- .of a sound reflecting material whose chief ingredients are afinely divided und deadening material intimately inter- 'mingled with a sound reflectingmaterial, and arelatively thin coating of a different 'soun'dfrefiecting material extending through outthe bore of the said hollow horn body.

11. A sound amplifying horn made-of a solid composition whose chief ingredients are finely ground infusorial earth intimately intermingled with a hinder, the proportions of the infusorial earth and the binder being such .that the inherent resonance of the binder is largel offset by the sound deadening property 0 the infusorial' earth.

Signed at :Chicago, Illinois, June 21st,

FRANK J. REICHMANN. 

